President Obama wants 'nuclear war with Russia'

US President Barack Obama has been accused of planning for a “nuclear war with Russia” by a protester during his speech.

The heckler accused the president during his speech to the Democratic National Committee on Friday.

"I'm sorry, who is that back there? What the heck are you talking about?" Obama responded to the heckler. "I don't know anything about that plan. I don't know what you've been reading."

On Friday, the US president warned his Russian counterpart Vladimir Putin over any military intervention in Ukraine.

Obama said he is “deeply concerned” by reports Moscow had sent troops into Ukraine’s Crimea region and warned that “there will be costs.”

“It would be a clear violation of Russia’s commitment to respect the independence and sovereignty and borders of Ukraine, and of international laws,” Obama said. “And just days after the world came to Russia for the Olympic Games, it would invite the condemnation of nations around the world.”

The turmoil in Ukraine entered a new chapter this week when an arrest warrant issued for the country’s ousted leader.

Ousted President Viktor Yanukovych, who is reportedly in Russia, said he remained Ukraine’s legitimate elected leader.

Putin said on Friday that any military activities taking place in Ukraine were not intended to threaten the nation’s sovereignty.

Obama said Russia’s involvement could be “deeply destabilizing” to Europe and represent “a profound interference” in Ukraine.

“The events of the past several months remind us of how difficult democracy can be in a country with deep divisions,” he said. “But the Ukrainian people have also reminded us that human beings have a universal right to determine their own future.”